Sorting can be as simple as a single level sort, such as relevance or date, or extended to sort by metadata or category.
To add a simple sort:
ISYSSearch.Sort = isysSortRelevance
To add a metadata sort (on author):
ISYSSearch.Sort = "META_AUTHOR"
To sort on category, than by relevance:
ISYSSearch.Sort = Array(isysSortRelevance, isysSortCategory)